Prostanoid EP1 receptor as the target of (-)-epigallocatechin-3-gallate in suppressing hepatocellular carcinoma cells in vitro

Aim: To investigate the effects of (-)-epigallocatechin-3-gallate (EGCG), an active compound in green tea, on prostaglandin E-2 (PGE(2))induced proliferation and migration, and the expression of prostanoid EP1 receptors in hepatocellular carcinoma (HCC) cells. Methods: HCC cell line HepG2, human hepatoma cell lines MHCC-97L, MHCC-97H and human hepatocyte cell line L02 were used. Cell viability was analyzed using MTT assay. PGE(2) production was determined with immunoassay. Wound healing assay and transwell filter assay were employed to assess the extent of HCC cell migration. The expression of EP1 receptor and Gq protein were examined using Western blot assay. Results: PGE(2) (4-40000 nmol/L) or the EP1 receptor agonist ONO-DI-004 (400-4000 nmol/L) increased the viability and migration of HepG2 cells in concentration-dependent manners. EGCG (100 mu g/mL) significantly inhibited the viability and migration of HepG2 cells induced by PGE(2) or ONO-DI-004. HepG2 cells secreted an abundant amount of PGE(2) into the medium, and EGCG (100 mu g/mL) significantly inhibited the PGE(2) production and EP1 receptor expression in HepG2 cells. EGCG (100 mu g/mL) also inhibited the viability of MHCC-97L cells, but not that of MHCC-97H cells. Both EGCG (100 mu g/mL) and EP1 receptor antagonist ONO-8711 inhibited PGE(2) 4 mu mol/L and ONO-DI-004 400 nmol/L-induced growth and migration of HepG2 cells. Both EGCG (100 mu g/mL) and ONO-8711 210 nmol/L inhibited PGE(2)- and ONO-DI-004-induced EP1 expression. EGCG and ONO-8711 had synergistic effects in inhibiting EP1 receptor expression. PGE(2), ONO-DI-004, ONO-8711, and EGCG had no effects on Gq expression in HepG2 cells, respectively. Conclusion: These findings suggest that the anti-HCC effects of EGCG might be mediated, at least partially, through the suppressing EP1 receptor expression and PGE(2) production.